Influence of pH and annealing on the optical and electrochemical properties of cobalt (III) oxide (Co3O4) thin films

Cobalt (III) oxide (Co3O4) thin films were deposited on glass and FTO substrates using chemical bath deposition method at a temperature of 80 degrees C in the alkaline bath maintaining the pH values of 10 and 12. X-ray diffraction result reveals that the crystallinity increased with increasing pH and annealing. Scanning electron microscopy (SEM) revealed features of flower-like particles, which transformed into a needle and rod-like structures after annealing. The optical studies showed a higher absorption in the visible region, which decreases as the wavelength increases, energy band gap range of 1.3 eV-1.85 eV and a remarkable refractive index of 1.40-1.75. The electrochemical testing of the electrodes obtained the highest specific capacitance of 1567F/g, the energy density of 245.98 (Wh/Kg) and power density of 2.08 (W/Kg) for pH 12 annealed. Specific capacitances, power densities and energy densities values obtained from electrochemical studies suggest that the films are suitable for use as supercapacitors electrodes materials.